Carboxamidopeptidase is a neurohypophyseal hormone inactivating enzyme which has been purified 400-fold to homogeneity from the skin of Bufo marinus. This serine peptidase hydrolyzes the Arg8-Gly9-NH2 and Leu8-Gly9-NH2 bonds of arginine vasopressin and oxytocin, respectively, and can cleave a number of oxytocin analogs with residue replacements in position 8. In addition, carboxamidopeptidase can liberate several different amino acid amides from the C-terminus of model substrates and can hydrolyze ester substrates of both trypsin and chymotrypsin. The unusual primary substrate specificity of this enzyme, as well as the size and stereospecificity of the active site binding region, will be elucidated in considerable detail. Specific inhibitors of carboxamidopeptidase will then be developed based on this specificity. Various enzymatic and structural properties will be investigated including pH effects on kinetic parameters, the role of the free sulfhydryl group, and the amino acid and carbohydrate compositions. Studies on carboxamidopeptidase will be extended to include identification, purification, and characterization of this enzyme from mammalian tissues (rat). The possible role of carboxamidopeptidase in connective tissue turnover will be studied. Purified carboxamidopeptidase will be used in amino acid sequence determination of peptides which contain a C-terminal amino acid amide and will be used to detect and assay new, potentially biologically active, amidated peptides in brain extracts.